Huazhong Agricultural University revealed a new mechanism of transcription factor gmnac181 promoting symbiotic nitrogen fixation and nodulation salt tolerance of soybeans
By: Date: 2022-07-03 Categories: foodtechnology Tags: ,
Recently, the soybean team of the school of plant science and technology of Huazhong Agricultural University published an online publication entitled”gmnac181 promotes symbolic nodulation and salt tolerance of nodulation by directly regulating gmnina ex” in new phytologyPressure in soybean”. This study revealed the key molecular mechanism of NAC transcription factor gmnac181 promoting soybean nodulation by activating gmnina and nodulation signal pathway, and the new mechanism of gmnac181 as a molecular network node to coordinate the plasticity development of symbiotic nodulation under salt stress.
Soybean is the most economically beneficial grain and oil crop, and it is also an important basic and strategic material related to the national economy and the people’s livelihood. China is a major consumer and importer of soybeans, and the current situation of foreign dependence of more than 85%makes China’s soybeans face a serious crisis. Therefore, high yield of soybean has become a major national demand. Low yield per unit area is a”bottleneck” problem that limits the yield of soybeans in China. Because symbiotic nitrogen fixation can provide more than 65%of the required nitrogen for soybeans, it is also one of the determinants of high yield of soybeans. In 2021, China’s”14th five year plan” for the development of national planting industry proposed to further increase the planting area of soybeans by”developing soybeans in saline alkali land”, but the inhibition of salt stress on nodulation and symbiotic nitrogen fixation will lead to a substantial reduction in soybean production. It can be seen that improving symbiotic nitrogen fixation efficiency, especially salt tolerant and stable nitrogen fixation, is an important prerequisite for increasing soybean yield, and can also meet the major needs of sustainable agricultural development in China. Up to now, the genetic mechanism of soybean nodulation and stable nitrogen fixation under salt stress has not been analyzed.
Researchers screened the yeast two hybrid library with gmnsp1a, an important transcription factor of nodulation signal pathway, and identified the NAC family transcription factor gmnac181; The detection of expression level showed that the expression level of gmnac181 in root nodules at different developmental stages was significantly higher than that in other tissues, and its expression was significantly inhibited in the early stage of rhizobial infection; The results of functional study showed that overexpression of gmnac181 promoted the formation of nodules, and the number of nodules decreased significantly after down-regulation of gmnac181, indicating that gmnac181 is a positive regulator in the process of soybean nodulation; Through amino acid sequence alignment and transient transformation results in tobacco leaves, it was confirmed that gmnac181 has the possibility of simultaneous localization of plasma membrane and nucleus, and that gmnac181 has transcriptional activation activity in yeast cells; Combined with the detection results of gene expression level, the researchers further used chip qPCR, EMSA and tobacco instantaneous CO transformation system to confirm that gmnac181 can directly bind to the gmnina promoter, which encodes the core transcription factor of nodulation factor signaling pathway, so as to activate the expression of this gene. More importantly, gmnac181, which is significantly induced and expressed under salt stress, positively regulates the nodulation efficiency of Soybean under salt stress, and significantly enhances the resistance of soybean root nodulation to salt stress.
To sum up, in the long-term evolution of symbiotic nitrogen fixing plants, we need to constantly face the complex environmental turbulence of terrestrial ecosystems, such as salt stress. Plants with symbiotic nitrogen fixation characteristics need to make the most accurate judgment and coordination between nitrogen nutrition acquisition and stress. As a positive regulator of soybean nodulation and nitrogen fixation, transcription factor gmnac181 is more likely to be a protein due to”salt stress”, and it is also likely to be one of the key nodes in the above complex molecular network. Through the direct molecular regulation of gmnina, it can effectively maintain the nodulation and nitrogen fixation pathway under salt stress. The relevant results not only provide important data support for a comprehensive analysis of the molecular mechanism of salt tolerant and stable nitrogen fixation in soybeans, but also provide new modules and new ideas for cultivating new soybean varieties with high nitrogen fixation efficiency, especially under salt stress, stable nitrogen fixation and high yield, and finally make an important contribution to the improvement of soybean yield in China.
Wang Xiaodi, a doctoral student of the College of plant science and technology, is the first author of this article, and Li Xia, a professor of the State Key Laboratory of crop genetic improvement and the College of plant science and technology, and Wang Youning, an associate professor, are the co corresponding authors of this article. Chen Kuan, a 2018 undergraduate of the Academy of Plant Sciences, Zhou Miaomiao, Gao Yongkang, Huang Huimei, fan Yuanyuan, a master’s student, and fan Zihui, a 2016 undergraduate, also participated in the work. The research was supported by the National Natural Science Foundation of China, the national key research and development plan, the Lingnan Modern Agricultural laboratory project and the natural science foundation of Hubei Province.
[English Abstract]
  Soybean (Glycine max) is one of the most important crop worldwide. Under low nitrogen condition, soybean can form a symbiotic relationship with rhizobia to acquire sufficient nitrogen for their growth and production. Nodulation signaling controls soybean symbiosis with rhizobia. The soybean Nodule Inception (GmNINa) gene is a central regulator of soybean nodulation. However, the transcriptional regulation of GmNINa remains largely unknown. Nodulation is sensitive to salt stress, but the underlying mechanisms are unclear. Here, we identified a NAC transcription factor designated GmNAC181 (also known as GmNAC11) as the interacting protein of GmNSP1a. GmNAC181 overexpression or knockdown resulted in increased or decreased numbers of nodules, respectively, in soybean. Accordingly, the expression of GmNINa was greatly up- and downregulated, respectively. Furthermore, we showed that GmNAC181 can directly bind to the GmNINa promoter to activate its gene expression. Intriguingly, GmNAC181 was highly induced by salt stress during nodulation and promoted symbiotic nodulation under salt stress. We identified a new transcriptional activator of GmNINa in the nodulation pathway and revealed a mechanism by which GmNAC181 acts as a network node orchestrating the expression of GmNINa and symbiotic nodulation under salt stress conditions.
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